<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .content {
            border: 1px solid #000;
            height: 800px;
            padding: 20px;
        }

        .left {
            width: 200px;
            height: 100%;
            background: red;
            float: left;
        }

        .right {
            height: 100%;
            background: pink;
            float: left;
            width: calc(100% - 200px);
        }
    </style>
</head>
<body>
<div class="content">
    <div class="left"></div>
    <div class="right">right</div>
</div>

</body>
</html>
